Telephone signaling system



Dec. 12, 1944-. M. BASCOM 2,364,771"

' TE PHONE SIGNALING SYSTEM Filed 152137.28, 1942. 3'Sheets-Sheet 1 H MBASCOM INVENT FRANCIS A. HU BARD ATTORNEY Dec.'12,1 944. Hqm. BASCOM HAL2,364,771

R TELEPHONE SIGNALING SYSTEM 7 Y Filgd Na -128, 1942 s Sheets-Sheet 2FIG. 3

FIG. 4 1 56 4/ 47 3040 o -I 59 I 36 52 25 Q 49 la 77 INVENTORSI H.M'BASCOM f, FRANCIS AHUBBARD r 1 ATTORNEY 12, 1944. H BASCQM f 2,364,771

TELEPHONE SIGNALING SYSTEM Filed May 28, 1942 s Sheets-Sheet a FIG, /0

I T M BASCOM INVAN ZfRANCIS A. HUBBARD v ArroR/"vEr Patented Dec. 12,

- TELEPHONE sIcNALmG SYSTEM Henry M. Bascom, New York, N. Y., andFrancis A. Hubbard, MaplewoorLN. 1., assignors to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a corporation of New YorkApplication May as, 1942, Serial No. 444,772

15 Claims. (Cl. 177353 This invention relates to signaling-systems andparticularly to telephone intercommunicating systems of the type whereintelephone connections between calling and called subscribers stationsare established, under control of the calling subscriber, by means 'of akey-type sender or transmitter, which functions to effect thetranssta'tion-selecting signals which are characterized by variouscombinations of positive and/or negative direct current impulses overthe line wiresextending from the signal transmission station mission ofstation-selecting signals comprising various combinations of positiveand/0r negative direct current impulses, and wherein the various impulsecombinations are registeredat a signal receiving point by translatingdevices which selectively respond to the impulses which characterize thetransmitted signals and controlthe operation of station-connectingrelays.

Heretofore, there have been proposed telephone station-selecting systemsof the type wherein connections are established, under the control of acalling subscriber, by means of a rectifier-type key-sender whichfunctions to cause the transmission of various combinations of positiveand/or negative direct current impulses over a line extending to acentral point. The impulses thus transmitted serve to selectivelycontrol the operation of translating devices at the central point whichfunction to complete the connection of the calling subscribers telephoneto a particular called telephone. In order that a sufllcient number ofstation selections be possible to render such systems practicable it hasbeen found necessary,

to selectively operate signal receivingequipment at a signal receivingstation.

This object is attained in accordance feature 01' the invention by theprovision-"or a -key-type sender ofthe rectifier type which renintransmitting certain of the station identifying impulse combinations, toutilize signal paths comprising either line conductor and ground. Ob-

viorusly, such systems require a suitable ground connection at thesignal transmitting; or calling .subscribers station.

In U. s. Patent No; 2,278,410, issued April' '7.

1942', to Henry M. Bascom et al. there is disclosed an executivetelephone call system in which oppositely poled rectifiers are adaptedto beconnected singly or in combinations, between each line wire andground at the subscriber's station to efiect fifteen distinct stationselections. This system functions satisfactorily and serves the purposefor which it is intended in all cases where a suitable ground connectionis available at the l telephone subscribers stations. Under someconditions, such a suitable ground connection at the subscribersstations is not available.

g It, isthe object of this invention to obviate the need-tor agroundconnection at the subscribers station'soi a telephonesystem in whichtelephone connections, betweencallingyand-called.subscrib-, ersfstationsare established under the control of:

the calling subscriber-,3 by the transmission of";

December giiifl ders it possible for fifteen distinct station-selectinssignals to be transmitted over the metallic loop which interconnects thesignal transmitting and receiving stations. More specifical y, this ob-Jeet is attained by incorporating in a rectifier-type impulsetransmitter, mechanism which functions to provide independent operationsof the rectifierconnecting means for each of the down and upstrokes ofthe individual keys of the impulse transmitter. Such a structure rendersit possible to connect one or more rectiflers between the two line wirestwice for each complete operation of a station-selecting key. I In thismanner, certain of the keys of the transmitierffunction to cause the tonof two pulses, or two groups of pulses consecutively over the metallicloop'for a single complete operation thereof.

Another feature of the invention resides in a particular form of signalreceiving circuit which distinguishes betweenimpulses transmitted duringthe down-stroke of the keys of a key-type sender and impulsestransmittedduring the upstroke of the keys.and which iimctions to register thesignals thus transmitted. A further feature of the invention'resides ina signaling system in which more than one signal may be characterized inthe same manner, and in which discrimination between signals having thesame characterization is obtained by transmitting one'signal during oneportion of a signal-trans mitting period and another signal during adlflerent portion of the. signal-transmitting period.

Before entering into a detailed description of the circuits andapparatus disclosed in the accompanying drawings, which areillustrative. of"

h ifi of n w mul e a e r m re l umma n n a mm. sw m.

. stroke of certain other keys.

code bar functions to operate the second-men'- tioned set of contactsprings during the downstroke and an up-stroke, and the code bar areactuated by the button during its down-stroke and are restored to normalwhen the button is" released, by means of restoring coil springs,

there being one such spring for each bar. Each of the four code bars isprovided with an integral, inwardly projecting arm which carries at itsextreme end a pawl. Each of the four pawls cooperates with a particularone of four ratchet wheels in such amanner as to cause the rotation ofits corresponding ratchet wheel through- ,an arc of 90 degrees, eitherduring the down-- stroke of a key, or button, or during the upstrokethereof. For example, two pawls, assigned respectively to two particularcode. bars, are effective in rotating their-corresponding ratchet wheelsonly during the down-stroke of the key, and are ineffective to rotatethe ratchet wheels duringthe up-stroke of the key. Similarly, two otherof the pawls, individually assigned to the other two code bars, areeffective in rotating their corresponding ratchet wheels only. duringthe up-stroke of a key, and are tneffective to rotate the wheels duringthe downstroke of the key. In this manner an number,

pending upon the number of code bars actuated by ,the key. p Two of thefour ratchet wheels are fixed to one section of a composite barcomprising a cy-.

lindrical portion and aportion having a square cross section, the twoportions being coupled by a coil spring so that the portion havingthe'flat surfaces lags slightly behind the cylindrical portion when thelatter is rotated. In other-words,-

the rotational movement of the cylindrical portion is transmitted to thefiat-sided portion through the coupling spring. As each ratchet wheel isrotated, the compositebar is similarly actuated. The flat-sided sectionof. the bar nism'when one of the actuating buttons, or keys one to four,of the ratchet -'wheels may be operated'durlng a complete operation of akey de-- disconnected until the actuated key is restored to normal. Thisinsures the disconnection of the telephone set from the mission ofimpulses. 1 t

, Reference will now be made to the acco panying drawings, in which:

Fig. 1 is a perspective view of a telephone set equipped withfifteenbuttons arranged in accordance with applicants invention; Fig. 2 is ageneral view of the apparatus which is housed in the telephone set shownin Fig. l, andthe mechanism .controlled by the buttons locatedexternally of the set, as shown in Fig. i;

Fig. 3 is a side view of the telephone set shown in Fig. 1 with part ofthe housing broken away to show details of the button-controlled orkey-' controlled switching mechansim;

Fig. 4 is a fragmentary side view of the telephone set shown in Fig. 3and illustrates the position of the switch contact controlling mechalineduring the trans is operated; 1

.Figs. 5, 6, 7 and 8'are enlarged fragmentary I views of the contactcontrollingmechanism."

Figs. 5 and 6 illustrate the positions of the down and; up ipawls justprior to the actuation ofa 1 station-selecting button and in reality,constitute enlarged views of the contactactuating mechanism inthe normalposition shown in Fig. 3. Figs. 7 and 8 correspond to Figs. 5, and 6 butshow the contact operating mechanism after a station-selecting buttonhas been depressed. In

' to register the impulses transmitted during the functions to operatecontact springs which convaristors between the second composite bar ofthe same construction as the bar described in the preceding paragraph,and serve to actuateza second set of contact such that one particularcode 1-bar functionsatn effect the operation of the first-mentioned setof contact springs during the downstroke of cer-- tain keys, and asecond code bar functions to operate the same set. of springs during theupsimilarly. third stroke-of still other of the keys, and"the fourthcode bar serves to efiect the actuation'ofthe same second set of contactsprings during the. un-stroke of the remaining keys. The key-typetransmitter is also equipped with a smaller U-shaped bar which isoperated when- 7 ever any one of the code-bars is actuated. ThisU-shaped bar functions to open a set of normally closed contacts whichcontrol the connection 01' the subscribers telephone set to the line.Thus,

, whenever any one of'the station-selecting keys, or buttons, isactuated, the subscribers telephone varistors between .eration. I

. Referring-now to Figs. 1 to 9, inclusive, of the operation of thestation-selecting buttons shown in Fig. 1. In this figure, thecontact-controlling mechanism is schematically illustrated at the leftof the vertical broken lines;

Fig. ll is a circuit diagram similar to Fig. 10. except that'agas-filled tube type of receiving circuit is;shown instead ofanall-relay typ and Fig. 12/ is a table showing the variouscontactcombinations which are efi'ecteddor the actuation of each button,or key, and they correspond-' ingcode relays which respond toeach keyopdrawings, the subscriber's telephone consists of a handset I' mountedon a cradle 2' formed inte'grallly with the housing a of the telephoneset, the housing being sulpported on a base plate 4'. .On the frontsurface "of the housing 3 is shown the usual dialmechanism 6 and fifteenbuttons i arranged in a single row I below the dial. Immediatelyin frontof the row of buttons, and fixed on th housing 3 is a transparent plateIt under which the designations correspondingto the individual buttons,orkeysmay-be placed. In Fig.- 2 is shown .the'general arrangement ofthe-apparatu housed insidethe telephone set.

This apparatus comprisesa ringer H; induction coil ii; a switchingcontact arrangement is controlled in the usual manner by the handset Iwhen placed in the cradle 2', or removed there from; the dial 8;button-controlled U-bars or levers Ii; the groups of contact springscontrolled tons. I

Each button consists of a cylindrical portion 26 (Figs. 3 and 4)protruding through an open ing in'the inclined front portion 2| of thehous ing 3. The button is provided with a flange 22 that abuts the innersurface of the inclined portion 2| of the housing 3; with an innercylindrical portion 23 of larger diameter than the cylindricalportion20; and with a cylindrical portion 24 of somewhat lesser diameterthan the portion 23'. A helical spring 25 is wound around the shankportions 23 and 24 of the button so that cause a correspondingcombination of bars l5 to berotated about the pivot pins 30 and 32.

Also supported between the ear-like append ages 40 of the bracket 3| isa short U-shaped bar 46 which is adapted to be rotated about the pivotpin 39. This bar 46 is located under the integral projections l5 of thebars l5 and is adapted to be rotated about the pivot whenever any one ofthe bars-or levers I5 is actuated. This U-bar also carries an integralprojection which extends inwardly from the pivot pin 36 and has fixedthereto, at its end, an insulating stud-41 which, when One nd thereofabuts the flange 22 and the other end abuts the mounting plate l8secured to the front portion 2| f the telephone set. The shank portion24 protrudes through an opening in the mounting plate 3 so that thebutton may be caused to-move axially downwardly in the opening, oraperture in the mounting plate 8 when the button is'manually depressed,and is-caused to return to normal position by therestoring ac-- tion ofspring 25. The normal position of the buttonis determined by the flange22 and the extent to which it may be depressed is determined by theshoulder formed at the'junction of the shank portions 22 and 23 and itsengagement with the plate I8.

,The buttons control the operation of four levers, or code bars lv (Fig.2) which are substantially U-shaped and arelocated at the forward end ofthe telephone set. Each 'bar consists of an elongated (portion extendingsubstantially the entire width of the base plate 4'-, and a right-angleextension 5' integrally formed with the elongated portion and located ateach extremity thereof. As shown in Fig. 2, these exa tensions areprovided with apertures which accommodate the pins 30 and 32, the pin 30serving the extensions IS on the left, and the pin 32 serving theextensions |-5' on the right, looking towards the front of thetelephoneset. The. bars are thus mounted for rotation about the pins 36and 32. ear-like appendages 46 of a spider-like bracket 3| which issecured to the base plate 4 by means of rivets 3|. as clearly shown inFigs. 3 and 4. The pin 32 is supported in. a; similar manner by thebracket 33 shown in Fig. 2, which is similarly secured to the base plate4'. The'left-extensions' l5 of the two lower bars I5, when-viewed fromthe front. of the telephoneset, are each provided with an integralprojection .which extends in-.

The pin 3llis supported between two the bar 46 is operated, engages anextension of the contact spring 49 and disengages the spring 48 from itsmate spring 49. Thus, whenever any button is depressed, the normallyclosed contacts of springs 46-49 are opened for a purpose to behereinafter explained.-

The bracket 3| is provided with two integral horizontal projections 56,both of which are shown in Fig. 2, and only one of which appears inFigs. 3 and 4, which support a rod or pin -5|.

This rod serves as an anchorage for one end of each of a plurality ofcoil springs 52 whose other ends are individually anchored to theinwardly projecting arms of the U-bars I5 and 46, such as the arms 4|and 42. These springs function to restore the U-bars |5,and 46 to normalposition after the manual depression of the corresponding buttons. Thebracket 33 is similarly provided with a pair'of horizontal projections53 and 54 whic h serve to support the rod or pin 55,

which provides a means for anchoring one end of springs, similarto thesprings 52, the other ends of which are secured to the inwardlyprojecting arms 43 and 44 of the U-bars l5. These springs also serve torestore the U-bars l5 1; normal after actuation.

At the outer extremity of the arm-4| there is pivotally mounted, at 56,a pawl 51. This p'awl may be associated with the arm 4| by means of ascrew 58 as clearly shown in Fig. 9. Similarly, the. outer extremity ofthe arm 42 pivotally supports a pawl59. The screw 60 serves to associatethe pawl 59 with the arm 42. The pawl 51 is provided at its lower endwith a dog 6| pivotally supported on the pawl at 51. The pawl 5.9

The pawl 51 may be characterized as a "down I pawl and the pawl-59 as an-up pawl, since these pawls perform their respective functions wardlyfrompivot pin 36, the functions of which be set forth in greater detailhereinafter.

These projections are identified by the numerals 4| and 42. Similarly,the rightor lower extensions l5 (Fig. 2) of the two upiper bars|5 are.each provided with an integral projection which extends inwardly fromth pivot pin 32., the func. tions of which will be describedhereinafter.

These extensions are indicated by the numerals 43 and 44. (I

The elongated portions of the U -bars |5are provided with projections orfingers, such as 36.

31, and others located in various positions throughout the length of thebars. Some of these.

projections are bent inwardly and others project button is depressedfacrtain numberfdfthe prow ss- Such as a 1,; p been??? a during the downand u strokes, respectively, of certain of the buttons as will be fullydescribed hereinafter. The bracket 3| is provided with two vertically.spaced projections 64 which support a rod 65. The rod 65, viewingparticularly Fig. 9, consists of a cylindrical portion to which thenumeral 65 is applied, and a portion 66 having a square cross section.The portion 65 is coupled to the portion 66 by means of a coil spring61, the purpose of which is to introduce a time lag between therotational movement of the portion 65' and the portion 66. The rod iscapable of rotational movement under the action of the pawls 51 and 59as will appearprsently. 1

Fixed to the rod or shaft65 near its left end, viewing Fig. 9, there aretwo ratchet wheels 68 and 69, each of which is provided with four teethf displaced ab ut thfep iiatfeo-d re inttervals'. As shown in Figs. 5and-;6,'*which-illus- I *trate the pawlfand ratchet arrangementsiii'their normaljpositions,the dogi6| or, pawl 51 lien 16- With respectto the ratchet teeth that, as

4 the pawl is moved upwardly under the action oi a button, the edge ofthe dog engages the tooth l 'and ..causes the ratchet wheel. 88 torotate through 90 degrees in a clockwise direction. The

position of the, dog BI and ratchet tooth it after the down-stroke of a.button has been completed 3 aces-r21 is illustrated by Fig. 7. The pawl59', as hereinbefore described, has pivotally associated there- .withthe dog St; the pivotal association being efie'cted by the pin 62. Thepin 62 also serves to support a pair of substantially triangularlyshaped member H which are integrally joined' atone end'to effect,substantially, an enclosure for the ratchet Wheel 68. The integral unionis ciation of the spring-supporting enclosure eiiected by members II and12 and the V-shaped dog consisting of the projections 6i and 14, withthe pawl 51, which association is effected by the pin 62, whenever thepawl is raised in consequence of the depression of a button, the enclosure is rotated on the rod 65 and the dog element 6! is.-similarly movedto cause the ratchet Wheel 68 to be rotated. The position of the spring18, as well as that of the dog elements 6i and I4 after the operation'ofa button is illustrated in Fig. 7. v

Referring now particu'larlyto Figs. 6 and 8, the

pawl'59 which heretofore has been referred to I the enclosure portions15 is associated with the pawl 59 by means of the pin 83, assumes theposition shown in Fig. 6. When a button is de-' pressed so as to raisethe pawl 59, the enclosure, comprising elements 15 and I6 and spring TI,to-

gether with the dog- 62 are moved so as to assume the positions shown inFig. 8. It will be noted that the edge of the dog 62 has moved to such aposition-relative to the ratchet wheel 69, as to be in readiness toengage the tooth 80 when the actuating button is released, and the U-bar5,

with which the pawl 59 is associated returns to,

normal under the action of its restoring spring 52. Thus,.during thedown-stroke of the button. the dog 62 rides over the curved periphery oftooth 80 of ratchet wheel 69 without efl'ecting, any

movement of theratche't wheel, and during the up-stroke orthe button,thedog 62 causes the ro-' tation of the ratchet wheel 69 through 90degrees. From the description thus far advanced, it is apparent thatwhenever a button or key is depressed so as to operate a U-bar I withwhich the down" pawl 51 is associated, the ratchet wheel 68 is rotatedthrough an arc of 90 degrees.

Similarly, when a key is depressed so as to op-v erat'e a .U-bar withwhich thefupf pawl 59 is associated, the ratchet wheel 69 remainsstationary, and during the return stroke otthe button,

the ratchet wheel 69. is rotated through an. arc

.- of 90'degree's. It is well at this time to indicate that though thepawl 51 functions during the down-stroke-of a key "orbutton to rotatethe ratchet wheel 68 through an arc of 90 degrees, the dog 6! does notcause the actuation of the ratchet wheel during. the, lip-stroke of thekey; though the pawl 61 is moved downwardly to its normal position atthat time. That this. is the case is apparent from an'examination ofFig. "l

which shows the dog 6| in the position it occupies just prior to therelease of the actuated button.

,The mechanism just described, which functions when the U-bars IS, withwhich the projections 4| and 42 are associated are operated, is duplicated at the bottom of Fig. 2, (or at'theright oi the handset interior,Fig. 2) so that the same ratchet wheel operations are eflected by the U-bars IS with which the integral extenions 43 and '44 are associated.Thus there are two U-bars I! which are efiective in rotating a ratchetwheel during the down-stroke of certain buttons and two which: areeflective in rotating a ratchet tioned portionof the rod!!! which iscontrolled through the medium of the U-bar extension 43' and 44. Theselsimilarly mounted on the bracket 33 shown at,

' the various mechanical operations which follow" wheel during theup-stroke of certain other buttons. More specifically, the U-bars I5with which the integral extensions 4| and 43 .are associated vfunctionto operate a ratchet whe'eLduring the down-stroke of a button, and theU-bars [5 with which the integral extensions 42 and 44 are associated'function to effect the rotation of a ratchet wheel during the up-strokeof a button.

As shown to the right of Fig. 9, the section 66 of the ratchetsupporting bar is operatively associated with a contact spring 82, whichspring 82 is adapted to -be moved into engagement with the contactspring. 83'. As the bar section 68 m tates under the action or the pawlsB'Iand 59 it serves as a cam to move the spring 82 into engagement withthe spring 83 in such a manner that the contact spring 82 and are inengageinent during a portion of the rotational movement-of bar section66 and are disengaged before the bar section completes its -degreerotation.

It is understood that a similar set of contact springs is' locatedat'the bottom of Fig. 2 to be actuated in a similar manner by thesquare-seccontact springs are indicated by the numeral 9i.

.As clearly disclosed in Fig. 3, the bracket 3| serves as a support forthe spring. pile-up 92 which includes the springs 48, 49, 82 and 83. Thespring pile-up 93 which includes the spring 9| is the bottom of Fig. 2.

In order to more fully explain the operation of the key, or button-typesender described above,

the operation of. several of the keys will nowbe described. It will beassumed that the button a to the extreme left-of Fig. 1 is depressed andreleased and that this button causes the operation of only the outermostU-bar l5 (Fig. 4) by virtue of the engagement of the bottom of the shankportion 24 with a single projection 31 associated with the U-bar. TheU-bar i5 assumes the position illustrated in Fig. 4 and by virtue oi theengagement of the integral projection ll thereof with the smaller U -bar46, the insulating stud 41 engages the contact spring 48 and disengagesit from the spring-49. The purpose of these contactsprings will appearfrom a description of the circuits of Figs. 10 and 11 to be madehereinafter. At the same time, the integral extension 4|, of theactuated U-bar I5 is moved upwardly by virtue of its pivot support 80.In mov-- ing upwardlmthe arr'n 4| pulls the pawl l1. up-

,closed.

Should a key or button be actuated which and/or 8|, respectively.

wardlycausingthe dog 8| associated. therewith causes the latter torotate through the same arc. 1

The rotational movement of the bar 88 is trans- In Fig. ortne disclosurethe key-sender located at the transmitting station, which may 1 be atelephone subscriber's station, -is indicated mitted to. thesquare-sectioned portion' '88 through the coupling effectedby spring 81so that the portion 88 rotates 90 degrees, its rotational movementlagging slightly behind that of the bar 85. In rotating through an arcof 98 degrees, the square-sectioned portion 68 causes contact spring 82to approach, engage, and disengage the contact spring 88 for a purposeto be described hereinafter. Thus, during a portion of the down-strokeof the button, the contact springs 82 and 88 are closed'and before thebutton reaches the lower limit of its down-stroke these contacts areopened. This sequence of contactoperations is produced by the squareperiphery of the rod section 88.

. When the button is released, it is restored-to normal under the actionof its associated spring 28, and spring 52 associated with the actuatedU- bar functions to restore the actuated U-bars Thus, the U-barextension movesdownwardly and during the downward movement thereof theele.-- ment 8I moves back over the surface of the ratchet wheel 68 toassume a position under the next succeeding tooth 85 in preparation. fora schematically at K. In this' showing, the controlling contacts areidentified by the letters A and B. The contacts A correspond ;to thecontacts 82-88 in Figs. 3 and 4, and the contacts B are intended tocorrespond to the contacts indicated at 8| in Fig. 2. Since each ofthese contacts may be operated during the up-stroke or the down-strokeof a. key, applicants have illustrated, in the schematic illustration,'two' other pairs of contacts 'D ,,D= and U and U,- the D designationindicating that the contacts D and D engage with contacts A and B,respectively,

during the down-stroke, and the U designation g indicating that thecontacts U and U engage with contacts A and B, respectively, during thesubsequent key operation. During this return movement, the ratchet wheel88 remains stationary. Thus, for a complete operation of the key,

or button' a, which includes its down-stroke and its up-stroke,'thecontact spri gs 82 and 88 are actuated-once. Obviously, when theactuated U- bar returns to normal, the auxiliary U-bar 88 re- B,respectively.

depressed,.it is assumed, in accordance with the schematic showing ofthe key-senderK, that the contacts D and/or D approach and engagecontacts A and/or B,- respectively, while during the up-stroke of a keythe contacts U and/or U approach'and engage the contacts A and/or Beforeentering into a detailed description of the operation of the systemshown in Fig. 10, it may be welLto mention the particular sequence ofcontact operations which is followed for a compiete operation of a key,that is, for a combined down-stroke and up-stroke thereof. Normally,

' the circuit is as illustrated. The rectiflers V and V= areopen-circuited and the line loop is open at the contacts of the"subscriber's telephone set.

' When the telephone set-is'removed from its supstores under the actionof its individual coil spring and the contact itself opposite the tooth88 thereof, During thisdownwardmovement of the key orbutton, .theratchet wheel 88 does not rotate and the contact springs 82 and88reinainiunactuated. The cori-v tact springs 48 and 88, however, are.diseng'agedi When the button is released, a spring 82 restores theactuated U-bar' to normal, that is, the

springs 88 and 88 are again.

arm 82, is moved' downwardly causing the dog 82.

to engage the tooth 88 of the ratchet wheel 88 and move the wheelthrough an arc of degrees. The bar section-88, accordingly, is-rotatedduring the up-stroke of the key or button to close the contact springs82 and 88.

By virtue ofthe fact that certain of thebuttons -or keys engage two ormore of the U-bar pro- Jections 88, 81, itis apparent that more than oneU-bar, and up to four, may be actuated in response tothe operation of abutton. Under these circumstances the U-bars associated with theintegral proj ctions I and/or 48 function during the down-stroke of thekeys flbpperatethe contact springs 82 88, and/or 8|, respectively,

while on the up-strqke of the keys the U-bars associated'with "theintegral projections l2-and/0r 88 function. to operate the contactsprings 8288 The operation of a. signaling system involving ings will.now be described.

port, the line loop is closed through'the subscribers substation set byway 'of the contact C.

Contact G corresponds to the contacts 48-18 of,

Figs. 3 and 4. ,As soon as a key starts its downstroke, thecontact C isopened as described hereinbefore'and this openingis, or may be, immedi-'atelyfollowed by the closure of the line loop through either one or bothrectiflers V and W and resistance R. The opening of the contact Cdisconnects the telephone subset from theline L. Just as a key reachesthe end of its down-stroke,

theline 'loop is completely opened, that is,. contact cremains open andtheactuated contact A or B reopens During the up-stroke of a key,

the line loop is, or may be, again closed throughrectifiers V or V,singly or in combination, and

resistance R. 1 As the key reaches its normal position, the-line:loop'is -closed through the subscribers subset owing'to the closure ofcontact G,;it being understood that the key-sender is so designed thatcontact C opens upon theactuation of any key and remains openuntil thekey resumes its normal unoperated position. Thus the subscriber's set isdisconnected from the line lpulsing. Located at the receiving station,orcentral omce, is an ail-relay receiving circuit which .is,

' supplied with power from the alternating current source'll8 by way ofthe transformer III.' The designated I88 and 188.

receiving equipment comprisesjfour code relays,

designated L1, 8 and 8, and two control relays,

nected in pairs across ,single oppositely poled rectiiiers. I with thepair of relays co'ns I88 and I88 are connected in a-full-waverectiflercircuit comprising. the'rectiflers Ill-,1", H8,

and Ill. The circuit arrankementissuch that The code relays are con-Rectifiers I81 and I88 are associatedg of relays I and 2-, and rectiflers H2 and H8 9. associated with the pair of relays l and 8. The controlrelays irelays'l andregister the impulses transmitted during thedown-stroke of the keys of the key.

sender, while relays-2 and 0 register the impulses transmitted duringthe up-stroke of the keys. Furthermore, relays I and 2 register thepositive direct current impulses, while relays 4 and8' register thenegative impulses.

Control relay I05 is marginal-and will operate 0 when the line loop. isclosedithrough the subscribers subset S, that is, when the subscriberremoves thetelephone set from its cradle "support, but will not holdoperated when resistance R is connected to the line. The resistance R isconnected in series with the recttfiers V and W relays I, 2, 0 and 8 toreceiyethe transmitted signals by removing a short from therectifiers mand I I2. This short is effected at the front contact and inner armatureof relay I05. At its outer armature and back contact, relay I05 proyideslocking battery for the impulse receiving v relays. 1

Control relay I03 is made slightly slow to opindicated, relayI05'operates under this condition. The circuit in which relay I05operates may be traced. as: follows: during the first half-cycle ofclosed contacts 0, through the subscribers suberate and to release. It-is more sensitive than relay I00 and will hold operated through resist-.ance R, but-will release when the loop is completely openedv at the endof the down-stroke of .the individual keys. Relay I00 serves to transfercurrent from the source 0, the-upper terminal. of the secondary windingof transformer I I I may be assumed to be positive and the lowerterminal negative, so that the circuit extends from the j upperterminalof thesecondary of transformer II I, through rectifier II5, winding ofrelay I05, rectifier, H0, over the tip conductor of line 'L,

set 8, ring conductor of line L, rectifier I01, back contact andjleftarmature of relay I03, operating winding of relay 2, rectifier I I2 tothe lower terminal of the secondary winding of transformer III. on thenext half-cycle, the circuit may be traced from the lower terminal ofthe secondary winding of transformer III, rectifier II3, oper-' atingwinding of" relay-0, right armature and back contact of relay I03,rectifier. I09, ring conductor of line L, through the subscriber's setS;

closed contacts C, tip conductor of line L, recti- I fier H4, winding ofrelay I05, rectifier II' to the upper terminal of the; secondary windingof transformer III. Relay-I05, therefore, operates on the rectifiedaltemating' current'traversin'gthe circuits just traced. Relay. I03being connected in parallel with relay I05 also operates in thesecircuits a short intervalafter relay I05 operates. The operating'windings of relays 2 and 0 being included, each in one'of the circuitsjust traced, these relays may operate. but will release 4 immediately.upon the "operation; of .relay I05.

the registrationcircuit from the down-stroke re lays I and lto theup-stroke relays 2 and 0;

The code relays will serve to transfer the codereceived, to selectivelyoperated mechanism such as station-connecting relays to connect thecall- I00, i'urthermore,' if released, will not operate throughresistance R, but if operated, will hold operated when resistance R isincluded inthe signaling circuit.

When any key of the key-sender at the'calling,

or code transmitting station is depressed. the first result is therelease of relay I05. Then according to the U-bars I0 selected by thekey, the down ing subscriber to the called subscriber as described .inthe above identified Patent 2,278,411). Relay 0' stroke registrationwill be recorded by relays I or 0, or by both or neither. At the end ofthe down-stroke, relay I00 will release, shorting relays I and 4 andremoving the shorts from relays 2 and l which relays will then beavailable -to receive the code registration on the up-stroke of the key.1 when the key restores to normal therelays I, 2, 0 and 0 return totheir normal condition.

' A description of the-operation, of the system shown in Fig. 10 willnow be made. Itis deemed unnecessary to describe. in detail theoperation of keyof the key-sex tier, and that 'a thorough understandingof the operation of the system will be had from a description involvingthe operation of but a few of the keys.

"It will now be assumed that the subscriber at 1 the calling stationdesires to establish a telephone connection with a subscriber's stationto which the key 'ais individually assigned. The subscribenaccordingly,removes the telephone handset from its support and depresses the key aand thenallows it to restore to normal under the action of the restoringspring. Removal ofgthe handset. from its support closes the line loopIII ; the .sytem which "follows the actuation of each Theoperating'windings of relays I and 0 are short-circuited by thearmatures and back contacts of relay I03. l 1

, When the key is depressed, contact C is opened andremoves the subsetS'fromthe line loop caus- -ing relay I05.-to release. Relay I03 beingslow to release; holds, operatedsu'flicientlylong to permit the closureof either-contact A or B, orbo'th, by the actuated key a, to,reestablish the loop .circuit by way of resistance R, as .will' appearscribers telephone set from the line L.

e-opening of contact C is followed immediately by the closure of contactA effected by the operation of key a. In'the schematic showing ,of thekey-sender K in Fig. 10, the contact D is co tacts are considered to beout of-enga'gement, ,as shown. \This contact engagementpersistssubstantially untiLthe keya reachesthe end of its opened... 1

During the contact A, a circuit exists which may be .traced fromthe'upper terminal of the secondary wind-i of transformer III, rectifierIli, windings of relays I05 and I00 in parallel, rectifier IIS, tipconductor of line L resistance R, rectifier V}, con.- tacts D and A,ring conductor of line L, rectifier.

III'I', operating winding of relay I, left armature and front contact ofrela I 03', rectifier I I2, to the lower terminal of thesecondarywinding of transformer II I. Relay Ioperatesin this circuitand, at its left armature and front contact, looks] I j to battery atthe outer armature' and back con-I performs a switching functionwhiohmay be utilized to control theoperationot a station-con nectingswitching device in a manner known in the art.

presently. *Co'ntact "C, open, removes the sub-' 1 I no in engagementwith contact A, and all other downastrokegwhen the icon circuit iscompletely engagement of contact D with..-

tact-ofrelay I05. At its rightarinature, relay v the key 0'; reaches theend of its downthrough the subscriber's subset. As hereinbei'ore. 7;stroke, the line'loop'is completely'open so that to transmit astation-selecting impulse which is registered by the relay I.

With the return to normal of 'key a, the contact C is again closedcausing relay I05 to again operate to remove the locking battery fromthe relays causing the operated relays to release and restore theirarmatures.

It-will now be assumed that instead of actuating key a the callingsubscriber actuates key b inorder to efl'ect a different stationselection,

Relays'l05 and I03 will be operated as described hereinbefore.

. As soon as key b starts its down-stroke, the

contact C is opened to remove the subscribers set Relay I05 accordinglyreleases,

from the line. and relay I03 holds operated as described in connectionwith the actuation of key a. During the down-stroke of key b nooperation of the ratchet wheel 69 (Fig. 9) is eflected and therefore norectifier connection to the line results.

to be rendered-effective during thedown-stroke of the key.

When the key e is depressed, contact is openedand contacts D and lengage contacts A and B, respectively, of thekey-sender shownschematically in Fig. 10. While these contactsare in engagement,positive and negative current impulses traverse the line loop to causethe operation of code relays I and 4. The oper ating circuit for relay Iis the same as described in connection with the operation of key a.Relay 4 operates in a circuit which may be traced fromv the lowerterminal of the secondary winding oftransformer III, rectifier II3,front contact and right armature of relay I03, operating winding of coderelay 4, rectifier I09, contacts 3 and D rectifier V ,.resistance R, tipconductor of line L,rectifier H4, windings oi relays I03 and I05 inparallel, rectifier I I1 to the upper terminal of the secondary windingof transformer III. Relays I and 4 accordingly are operated when key eis actuated to register the signal transmitted by'this key.

I When the key e reaches'the end of its downstroke, the loopcircuit isopened causing the release of relay I03, but sincevno impulses aretransmitted during the up-stroke of key e, the

release of this relay performs no useful purpose in this particularinstance. -When the key e reconnect the subset S However, when the key breaches its lower limit, the line circuit is completely opened and relayI03 releases, shorting relays I and l and removing the shorts fromrelays 2 and 8 which latter relays are then available to register theimpulses transmitted during the up-stroke of key b. Durwheel 69 isrotated to-cause a closure of contact A, or contacts 8283 of Figs. Mind4. That is, referring to the schematic K of Fig. 10,. he contacts U andA engage each other during the I up-stroke'of key b. -During thisengagement a circuit may be traced extending from the upper terminal ofthe secondary winding of transformer III, rectifier .II5, windings ofrelays I05 and stores to normal, contact C is again closed to reto theline L and to reoperate relay I01),

The condition will now be described in which I impulses aretransmittedover the line loop during both the downand up-stroke's'of astationselectingkey. For this purpose it will befas- 'surned that the-calling subscriber actuates the stationgselecting key of It will benoted, by ref- 'ing the return or up-stroke of key b the ratchet I03 inparallel, rectifier II8, resistance R, rectiver V contacts U and A,rectifier I0], back contact and left armature of relay I03, operatingwinding of code relay 2, rectifier III to.

the lower terminal of the secondary winding of transformer III. Relay 2operates in this.circult and at its front-contact and right armaturelocks in an obvious circuit. At its left armature and front contact,relay 2 may control the operation of a station-connecting relay. Thus;'on the return stroke ofkey b, a positive impulse is transmitted overthe line and is registered by relay 2. When key b reaches its normalposition the receiving circuit is restored to normal andthe contact 0 isclosed to reconnect the subscribers telephone set to the line.

The station selections thus far described were effected by thetransmission of pulses of a sin- -gl'e polarity only, which weregenerated on the down-stroke of the key a and on the upj-stroke of keyb, respectively. It will now be described .how a station selection iseffected by the trans! mission of a signal comprising both positive andnegative current impulses generated during, thedown-stroke of a key. Forthis purpose; it will be assinned that the subscriber at stationS.actuerence to the table ,(Fig; 12), that both contacts A and Bfunction during the-down-stroke of key 9' and that only contact A isinvolved in the up-stroke thereof.

When the key 9 is depressed, contact 0- is opened and contacts D and Dengage contacts A and B, respectively. The engagement of contactsD and Dwith contactsA andB effectively connects rectifiers V 'and V,respectively, across the line L by way of resistance R in the mannerdescribedin connection with the oper atio'n of key e; Relaysl and 4-,accordingly, operate and 'lock, aspreviously described, during thedown-str'okeof key g. When the key g reaches the end of its down-strokesthe loop circuit is completely. opened as previously described, so

that relay I03 restores its armatures. Relay I03,

in restoring its-armature s, prepares relays 2 and 8 for the receptionof impulses transmitted fduring theup stroke of the'keym. During theup-stroke of key 9, contacts U 'and;A of the keysender K come intoengageinent' so that a positlve currentimpulse'traverses acircuitextending fromv theupper terminal of the secondary winding oftransformer l'll,'rectifler II5, wi'nd-' ings of relays {05 and I03inparallel, rectifier IIO, upper conductor ofline L, resistance R,rectifier V contacts UP and A of the key-sender, lower conductor of lineL,' rectifier 1, back contact and left armature of relay I03, operating-windln g of code relay-'2, rectifier lI2tothe lower terminal ofthesecondary winding of the transv former'II I. Relays 4, I and 2,accprdingly, re-.

ates the key e, which, in accordance with the table (Fig. 12) causesboth contacts A and 3 spondto the operation of key g of the key-senderstation corresponding to the key-g.

and cooperate .to eflec't the-selection of} called In describingtheoperations 'of the circuit, I

which follow the actuation of keys 0., b, e, and a, the followingconditions have been covered. I

- 1.- The transmission of a single pulse of positive-direct currentduring the down-stroke of key 'a. l

2. The transmission of a single pulse of posi-' tive direct currentduring the up-stroke of key b. 1 a

3. The transmission of a positive and a negative current impulse duringthe down-stroke of key 6.

) alternative to that shown in Fig. 10., The registration, or coderelays l, 2, 4 and 8 of Fig. 10,

can be made to operate on a half-cycle of curfore, that a fullhalf-cycle of each. polarity is included in the contact closures foreach'direction of operation of a station selecting key. For

. GO-cycle supply, which is the intended frequency of the supply sourceH in Fig.. 10, this would than the impedance of .the subset s: and willbe further increased to the full supply voltage when the loop is openedat the down-stroke ofa key. The-full secondary-voltage of transformer 13is applied to the control gap of the tube 225 associated with relay 205while-that applied to the tube 223 associated with relay 203 is reducedby the potentiometer 224. The batteries HI and 2, the Iormer of 130volts and the latter of 80 volts furnish anode potential for the tubes223 and 225.

The values are so chosen that neither tube breaks down as long ascontact C is closed, while the increased potential drop throughresistance R, when C is opened, is sufilcient to break down tube 225 andoperate relay 205. Relay 203 will operate only when a key reaches theend of its ing the full supply voltage at the terminals of require aminimum closure of about 20 milli-., I

seconds each way. vIn the key-sender illustrated in Figs. 1 to 9,inclusive, the necessary time .closure oi the contacts is insured by thecou- 'pling springs '61 which guarantees contact closuresof sufflcientlengths of time without imposing on .the subscriber any requirement asto the manner in which the keys of the key-sender are to be operated.Another way of coping with the situation referred to above is toincrease the supply frequency, so that a full cycle will occupy lesstime.

. rent of the proper polarity. It is required, theredown-stroke andopens the line loop thus applytransformer D. Relay 205 activates theregisary windings of transformers E and F, and provides an operatingpath for relay 203.

A description of theoperation of the receiving circuit shown in Fig. 11will now be made a, b, e, and g will be operated to effect fourdifferent station selections.

Prior to the operation of the key a. in making a first stationselection, the circuit elements are in the condition illustrated. Whenthe key a is operated, the contact C is opened in the manner previouslydescribed, to remove the telephone set S from the line. The operation ofkey For example, if a frequency of 200 cycles is used,

the minimum contact closurerequired would be slightly over 5milliseconds, which could be obtained without the introduction of thecoupling spring 61' in the key-sender.- However, this .would reduceproportionately the time ofoperation of the code. relays. The circuitshown in Fig. 11 has been dev ised to illustrate the use of a .supplysource designated 2I0,' which has a frequency of approximately 200cycles, and gastube type receiving equipment which has the speed ofoperation required at such a frequency.

The arrangement ofthe subset is the same as in Fig.10, and thefunctionsof the several' parts of the receiving circuit aresubstantially equivalent to those of the corresponding elements ofthecircuit of Fig. 10. The registration relays I, 2, 4 and 8 areoperated through-gas-fllled 3 tubes 230, 234, 233 and 235,.respectively,which look when operated.

Control relays 203 and 205 perform substantially the same functions asrelays 103 and I05,

' respectively, of Fig. 10 and have the samemar ginal discrimination.This discrimination is on an operate basis rather than a release basisas in the circuit of Fig. 10. The input transformer Dis bridged directlyacross the line loop L andthe 200-cycle supply 2| 0 is fed throughresistance 220. .Thusthe potential across the transformer D will be aminimum'when contact C is closed; 'will be greater when this contact isopened, since resistance Risconsiderably higher a causes contact.A toengage the contact D of the key-sender schematically shown at K, so

that the increased potential dropthrough re-.

sistance R is sufilcient to break down the tube 225 to 'cause'theoperation of control relay 205. The'control gap of the tube 225 extendsfrom ground, through battery 22I, control electrodes of tube 225,secondary winding of transformer D, through battery I to ground. Asindi- 'cated, the potential impressed on this tube is now of suflicientmagnitude to cause the tube to fire, so that relay 205 operates. Relay205 operates in a circuit extending from grounded 'battery 22I, main gapof tube 225 to the anode thereof, winding of relay 205v to groundby wayof condenser 250. The condenser 250 charges up at this time and whenrelay 205 operates the resistance capacity network serves to hold .relay205 operated for a small intervalof time before it releases. Resistance249 is used primarilyto prevent contact sparking.

rAt its armature, relay 205 applies ground potential to the point 25Iwhichis common to the secondary windings of transformers E and F. By

virtue of this ground. connection the registration circuit includingrelays L2, 4 and 8 beccmiesactivated. Relay 205 also supplies ground tothe anode circuit of tube 223 to prepare relay 203 for operation.

A circuit may now betraced from the upper terminal of the secondarywinding of transformer 2| I, upper conductor of the line L, resistanceR,

rectifier-V contacts D and A, lower conductor of line L, primary windingof" transformer E, rectiller 2", to the lower terminal of the secondarywinding of transformer 21 I. The voltage appearing acrossreslstance'221eonnected across the secondary winding of transformer Ecauses-the tube 230 to "iflre." The circuit for tube 230 extends fromground, battery 23 I; control electrodes of tube 230, back contact .andleft armature of tration circuit by putting ground on the second- -andfor this purpose it will be assumed that keys downstroke of key a and atits armature may coning of relay I, to ground by way of battery 253.

The circuit to'battery 253 is shown in broken lines to indicate thatthis circuit, in which the operated, tubes lock, may be controlled inany suitable manner so as to release and reset the register relays.

0 When the tube 234 operates, code relay';2 oper- While the lockingcircuit could be placedunder the control of relay 205, it might well becontrolled in some other manner, such as bya supervisory relay in thetelephone system.

Thus code relay I operates and locks during the trol the operation ofstation-connecting switching devices to eilect a connection to thetelephone line to which the key a is assigned.

When the key a reaches the bottom of its down-stroke, the line loop isopened causing the 9 application of the full supply voltage to theterminals oi transformer D. When this occurs relay 203 operates sincethe voltage now applied to the control electrodes of tube 223 is of sucha magnitude as to cause the tube to fire. remains. operated. Relay 203,operated, opens the circuits to the control electrodes of tubes 230 and233 and completes the circuits to the control electrodes of tubes 234and 235. Thus relays 2 and 8 winding of transformer E, rectiiler- 2Il,tothe lower terminal ofthe secondary winding of transformer 2Il.- Thus avoltage appears across re sistance 221 which causes the operation ofgastube 234. The circuit for tube 234 may be traced from ground, battery23I, cathode and control electrode oi" tube 234, front contact and leftarmature of relay 203, resistance 221, to ground by way of'the frontcontact and armature of relay 205.

ates in a circuit extending from battery 253, winding of relay 2, anodeand cathode of tube'234 to ground by way of battery 23I. Relay'2,operated, controls the operation of a station connecting relay, notshown, to'complete a connection'to the line towhich the key b isassigned.

-When the key 17 reaches its normal position, contact C is closed toreconnect the subset S to the line, whereupon the circuit is restored tonormal, as previously described.

When key 6 is actuated in initiating a call to a called subscriber'sstation, both contactsA and B are actuated on the down-stroke of the keyas ind cated by the table, Fig. 12. When this occurs,

Relay 205- 25 are rendered available to register the impulse transmittedduring the up-stroke of the key a. Which ofrelays 2 or 8, if either,operates depends upon the polarity of the transmitted impulse. As shownby the table, Fig. 12, no rectifierconnecting contacts are operated onthe up-stroke of key a so that the key restores to normal withouteffecting the transmission of an impulse during its return movement.When key a returns to normal the contact C is closed to reconnect thesubset s to the line. This reduces the potential 4 applied to thecontrol electrode of tube 225 andthe tube deionizes. Thecondenser-resistance network associated with the relay 205 serves tohold the relay operated for a brief interval of time (in the order of afew milliseconds) and then permits 4 it to release when the potentialapplied to the control electrode is reduced to a;value insufficient tosustain ionization. This reduction in potential occurs, as stated, whenthe subset S is reconnected to the line incident to the return of a-keya to its normal position. Relay 205, released, opens the anode circuitof tube 223 permitting this tube to deenergize and release relay 203.The circuit is now restored to its normal condition.

Should key I) be operated, contact C would open in a manner nowapparent, and relay 205 would operate as described in connection withthe operatlon of key a. Relay 205 prepares the register circuit for thereceipt of the transmitted impulses.

As indicated by the table, Fig. 12, no. rectifier con- 60 nectingcontact closure is effected during the down-stroke of key 1).. The loopcircuit is opened when the key reaches theend of its down-stroke.whereupon relay 203 operates in the manner hererelay 205 operates whencontact 0 is opened,- and code relays I and i iunctionto register thetransmltted' lmpulses. Relay I operates to register the positive impulsein the same circuit described'in connection with the operation of thisrelay followingthe actuation'oi key a, and relay 4 operates as a resultof the transmission of the negative impulse. The circuit for thenegative impulse may be traced from the lower terminal of the secondarywinding of transformer 2| I, primary winding of transformer F. rectifier2I2, lower conductor.

of line L, contacts B and l) of the key-sender K, rectifier V,resistance R, upper conductor of line L, to the upper terminal of thesecondary winding of transformer 29 5. Due to the current flow in 0primary'winding of transformer F, there is produced a voltage dropacross resistance 229 which results in the operation of tube 233. Thecircuit for tube 233 may be traced from ground, battery.

- 23I,cathode and controlelectrode of tube 233,

5 back contact and right armature of relay 203, re-

sistance 223,- to groundat the front contact and armature of relay 205.Code relay 4 now operates in a circuit extending from grounded battery253, winding of relay 4, anode and cathode of tube 233, battery 23I toground. Thus. code relays I and 4 --operate as a result of thedown-stroke of key e to register the signal characterized by thecombined positive and negative impulses transmitted.

These relays may be used to control the operation of switching deviceswhich effect a conhection to 7 the called lineto which key e isassigned.

inbefore described. With relay 203 operated.code

' that the key restores to normal without efi'ectcuit may be traced fromthe upper terminal of the secondary winding of transformer 2| I, upperconductor of the line L,- resistance R, rectifier V. contacts A and U ofthe key-sender schematically shown at K, lower conductor of the line L,primary A When key e reaches the end of. its down-stroke the line loopis opened causing control relay-203 to operate and to substitute coderelays 2 and ,0

for code relays I and 4 in their association with the line circuit,whereby code relays 2 and 0 are rendered available to register theimpulses, if any, transmitted during the up-stroke of key e. As indicated by the table, Fig. 12, no impulses are transmitted during theup-stroke of key e so ing any further contact operations. When itreachesits normal position, the'key e closes contact C to reconnect thetelephone .set S to the line which results in the release ofrelays 205and 203. v ,i

In the event key 9 is operated to eflect a connection between thesubscribersstation' at which the key-sender K is located and asubscriber's I line to which key 0 is assigned, contacts A and fortr B,as shown in the table, Fig. 12, function durv ing the down-stroke .ofthe key to transmit vapositive and a negative impulse over the line. In

response to these impulses code relays l and 4 operate in the samemanner as' when key'e was employed. When key g reaches the end of itsdown-stroke .the line circuit is opened to cause relay 203 to operate soas toprepare code relays 2 and B for the registration of the impulses,if any,- transmitted during the up-stroke of the key. As shown in thetable,-Fig. 12, the contact A .is employed during the up-stroke of key gto cause the transmission of a positive impulse over the 'line whichoperates code relay 2. It. is be-,

lieved unnecessary to describe in detail the circuits completed duringthe up-stroke of key 9 which result in the operation of code relay 2,since they are identical to those efiected during the up-stroke of key bpreviously described. Suffice it to say that relay 2, operated duringthe up-stroke of key g and -relays.l and 4, operated'during thedown-stroke of key g.function collectively to control the operation "ofswitchingequipment (not shown) which results in the extension of aconnection to the telephone line assigned to key g.

By referring to Fig. 12 it will be noted that certain signals effectedby the key-sender of this invention are characterized in thesame-manner. For example, the signals transmitted incident to theactuation of keys'a and b are each characterized by an impulse ofpositive polarity; also. the signals transmitted incident to theactuation of keys d and h are each characterized by an impulse ofnegative polarity; similarly, the sig-' nals transmitted incident to theactuation of I keys e and i are each characterized by a positive Thusmore than one signal is characterized in thesame manner.. The

and a negative impulse.

discrimination between signals having the same .characterization iseffected by transmitting one signal, such as the signals transmittedincident to the actuation of keys a, d and e during the first portion ofa signal transmitting period, whereas the'signals transmitted incidentto the betwee tion by ransmittingone signal during one-portion oi -asignaltransmitting period and another.- signal during adifl'erentportion oi the signal transmitting period.

What is claimed is:

1. In a signaling system in which a called sta-' tion is characterizedby a particular combination of impulses and in: which complementalportions of the station-characterizing impulse combination aretransmitted over a line consecutively home-calling station, a pluralityof keys at the calling station each having adown-stroke and an- 11-stroke, and means controlled by said keys mitting one portion of thestation-characterizing impulse combination over the line during thedown-stroke of a key and for transmitting the otherportion. oi thestation-characterizing impulse combination over the line during theup-stroke of the key. V

2. In a signaling system in whicha called station is characterized by aparticular combination I otpositive an d/or negative currentimpulses-and I current imp in which complemental portions of thestationcharacterizing impulse combination are transmitted over a lineconsecutively from a calling station, a key at the calling stationhaving a down-strokeand an up-stroke, means efiective" during thedown-stroke of said key {or causing the transmission over the line ofthe first complemental portion of the stationcharacterizing impulsecombination, and means effective during the up-stroke of said keyforcausing the transmission over the line of a second complemental portionof the station-characterizing impulse combination. V

3. In a signaling system in which a called station is characterizedbytwo groups ofpositive and/or negative current impulses and in which Ithe two groups of impulses are transmitted con- 'secutively over a lineextending from a calling station, -a signal transmitting key at thecalling station whose complete signal transmitting operation embracesboth itsdown-stroke and its up:

stroke, and means controlled by said key during v its down-stroke andits'u'p-stroke for causing the transmission 'of a difierent one of thetwo groups of current impulses.

4.,In a signaling system in which a station- 3 selecting signal ischaracterized by two separate groups of impulses, each of which is madeup of one or more positive'and/or negative impulses; a line, a keyhaving a doWn-stroke-and an up-stroke, and means controlled by said keyfor-transmitting one. of the groupsof impulses over said line during thedown-stroke of said key andv the other group of impulses during the jup-stroke of said key.-

' 5. In a signaling system in which a station; selectingsignalischaracterized bya particular combination 017;. positive and/ornegative cur- ,rent'impulses transmitted, in code, .over'a line. 40 8.keyh'av-ing a down-stroke and an up-stroke.

and means controlled by, said key mtransmitting, in code, a portion .ofthe signal-characterizing impulse combination only during thedown-stroke of said key and for transmitting;

in code, another portion of the signal-characterizing impulsecombination only. during the up-stroke of said key.

6. In a signaling system-in which astation identifying signal ischaracterized by two groups of current impulses, a sending station; areceiv- '-ing station, a key atsaid sending station having a down-strokeand an upl-strokejmeans controllednby saidkey during. its down-strokefor transmitting one of the gr ups of current impulses overthe line, and

eans controlled by said key during its up-stroke' for transmitting theother groupfof impulses over the line whereby the transmisslon of astation-identifying sig-: 'nal over said line is completed ,only whensaid key is operated through both its down-stroke and its up-stroke. c

' 'z. m combinationin a. system. a]

sending station, arecei'ving station} a two-'-wire line'inter-connectingsaid stations, asource 0! alternating current connected to, said line,means at said sending station for transmitting direct s from said sourceover said line, i a key 'at said sending station having a cycle ofoperation,whicli includes the down-stroke and the up-stroke thereof,means controlled by said key for connecting said direct current impulsetransmitting means tosaid-line during the downstroke or said key-andagain duringits .up-stroke.

' whereby-direct current impulses are transmitted consecut vely oversaid line, and means at said receiving station for registering theimpulses transmitted over said line.

8. In a signaling system in which two groups of positive and/or negativecurrent impulses are transmitted over a line consecutively tocharacterize a station-selecting signal, a key having the impulsestransmitted during the down-stroke f of said key and a group oftranslating devices for responding to and registering the impulsestransmitted during-theup-stroke of said key, and means controlled bysaid key for rendering each of said groups of translating devicesavailable to register the impulses transmitted during a correspondingstroke of said key.

9. In a signaling system in which a stationconnecting signaltransmitting and receiving stations, of a signal receiving circuitcomprising two groups of selectively responsive translating devices, asource of alternating current connected to the line, and means foreffecting the consecutive transmission of direct current impulses of.

Opposite polarities from said source over said line comprising akey-type sender including a plurality of manually operable keys, a pairof oppositely p'oled rectifiers', means controlled by a certain one ofsaid keys and effective during the down-strokethereof-for connecting oneof said 'rectiflers' between the two wires of. said line to cause thetransmission of a direct current impulse of one polarity over said linewhereby a certain one of the selectively responsive translating devicesof one of saidgroups is operated,

meanscontrolled by "said keywhen it reaches the end of its down-strokefor preparing theselectively responsive translating devices of the other5 of said groups for operation, and means conselecting signal ischaracterized by two separate combinations of positive and/or negativecurrent impulses, a key having a down-stroke and an up-stroke. meansvcontrolled by said key fdr transmitting the two separate combinations ofpositive and/or negative current impulses over said line consecutively,a group of translating devices for registering the combination ofimpulses first transmitted oversaid line, a group of translating devicesfor registering the combination of impulses next transmitted oversaidgroup of translating devices effective to register the first transmittedimpulses, and means controlled by said key upon completion of itsdownstroke for rendering the second said group oi translating deviceseffective to register the next transmitted impulses.

10. The combination in a signaling system in which certain signals arecharacterized by directcurrent impulses transmitted consecutively over atwo-wire line interconnecting signal transmitting and receivingstations, of a signal receiving circuit comprising two groupsof'selectively responsive translating devices; a source of alternatingcurrent connected to the line, and" '5 means for effecting theconsecutive transmission of direct current impulses from said sourceover the line comprising a key-type senderincluding. a plurality pfmanually operable keys, a recti-. fler, means controlled by a certainone of said keys and effective duringthe down-stroke thereof forconnecting said rectifier between the two wires of said line to causethetransmissi'on of a line, means controlled by said key when beginningits down-stroke for rendering the first said trolled by said key andeffective during the upstroke thereof .for connecting the other of saidrectifiers'between the two wires of said line to cause the transmissionof a direct current impulse of a different polarity over said line,whereby a certain one of the selectively responsive translating devicesof said other groupis operated. i

12. The combination in a signalingsystem in which certain signals arecharacterized by two groups of .direct current impulses, each comprisinga positive and a negative impulse, transmitted consecutively over atwowire line interconnecting signal transmitting and receiving stations,a signal receiving circuit comprising two groups of translating devices,each group including a device selectively responsive to impulses of eachpolarity;

a source of alternating current connected to the .line, and means'foreffecting the consecutive transmission of two groups of positive andnegative direct current impulses from said source over saidline,comprising, a key-type sender including aplurality of manuallyoperable keys, a

pair of oppositely oled rectifl'ers, means controlled by a certain oneof the keys of said sender and effective during the down-strokethereof-for simultaneously connecting both said rectiflers between thetwo wires of said line to cause'the transmission of a positive and a,negative direct current impulse over said line, whereby the translatingdevices of onset said groups thereof are operated, means controlledby'said key when it direct current impulse over said line to operate acertain one of the selectively responsive trans-. lating devices of oneof said groups, means controlled by said key: when it reaches the end ofits down-stroke for preparing the other of said groups of selectivelyresponsive translating devices for operation, and means controlled bysaid key and effective during the up-stroke thereof for reconnectingsaid rectifier between the two wires of said line to cause thetransmission of'a second direct current impulse over said line whereby acertain one of the selectively responsive translating devices of saidother group is operated.

11, The combination in a. signaling system in which certain signals arecharacterized by direct current impulses of opposite polaritiestransmitted consecutively over a two-wire line interreaches the end ofits down-strokefor preparing the translating devicesof the other groupthereof for operation, and means controlled by said key and effectiveduring the up-stroke thereof for reconnecting both said rectiflersbetween the two wires of said line to cause the transmission of a apositive and a negative direct current impulse over said line, wherebythe translating devices of the other of said groups thereof areoperated.

- 13. The combination in a signaling system, of a line, an impulsetransmitter comprising a key having a down stroke and an up-stroke andcapable of transmitting an impulse over said line for eaclr strokethereof, impulse receiving equipment for receiving the impulsetransmitted by said key during its down-stroke, impulse receivingequipment for receiving the impulse transmitted by said key duringitsup-stroke, and means controlled by said key for rendering saidimpulse a line; an impulse receiving circuit, and means for transmittingimpulses oversaid line to said impulse receiving circuit comprising apair of pulsing contact springs whose period of closure determines thelength of impulse transmitted over said line, a key, a sectionalized rodhaving one section thereof in operative association with said contactsprings and the other coupled to said key, whereby said rod is rotatedwhen said key is actuated to effect the closure of said contact springs,and means comprising a spring coupling the two sections of said rod,whereby the period of closure of said contact springs incident to theactuation of said key is renderedindependent of the speed of operationof said key.

15. In combination in a key-type sender for transmittingstation-selecting impulses of positive and/or negative polarities,singly or in combination over a line,.rectifying means for determiningthe polarity of the transmitted impulses, a

asea'm contact means for connecting said rectifying means to said line,a key having a down-stroke and an up-stroke, levers operativelyassociated with said key, a ratchet wheel; a pair of arms depending fromsaid levers and operatively associated with said ratchet wheel in such amanner ciated with saidratchet wheel for operating said contact meanswhereby said rectifying means is connected to said line once for each ofthe upand down-strokes of said key.

HENRY M. BASCOM. FRANCIS A. HUBBARD.

